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J/ApJ/661/1119      Spectroscopy in the 25 Ori group    (Briceno+, 2007)

25 Orionis: a kinematically distinct 10 Myr old group in Orion OB1a. Briceno C., Hartmann L., Hernandez J., Calvet N., Vivas A.K., Furesz G., Szentgyorgyi A. <Astrophys. J., 661, 1119-1128 (2007)> =2007ApJ...661.1119B
ADC_Keywords: Clusters, open ; Stars, pre-main sequence ; Radial velocities ; Equivalent widths Keywords: open clusters and associations: individual (Orion OB1) - stars: kinematics - stars: pre-main sequence Abstract: We report here on the photometric and kinematic properties of a well-defined group of nearly 200 low-mass pre-main-sequence stars, concentrated within ∼1° of the early-B star 25 Ori, in the Orion OB1a subassociation. We refer to this stellar aggregate as the 25 Orionis group. The group also harbors the Herbig Ae/Be star V346 Ori and a dozen other early-type stars with photometry, parallaxes, and some with IR excess emission, indicative of group membership. Description: We obtained low-resolution optical spectra of our candidate PMS stars with a variety of telescopes and instruments. The brighter stars (V~>16) were observed at the 1.5m telescope of the Whipple Observatory equipped with the FAST Spectrograph. For the fainter (V~<16) candidates in our photometric survey the bulk of the spectroscopic follow-up was done with the Hectospec multifiber spectrograph on the 6.5m MMT telescope at Mount Hopkins. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 82 78 Low-mass pre-main sequence members in our 25 Orionis and Ori OB1b Hectochelle fields
See also: J/AJ/131/2959 : Candidate low-mass PMS in 25 Orionis group (McGehee+, 2006) J/AJ/129/907 : New Ori OB1 members (Briceno+, 2005) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 3 I3 --- CVSO CIDA Variability Survey of Orion running number (1) 5- 6 I2 h RAh Hour of Right Ascension (J2000) 8- 9 I2 min RAm Minute of Right Ascension (J2000) 11- 15 F5.2 s RAs Second of Right Ascension (J2000) 17 A1 --- DE- Sign of the Declination (J2000) 18- 19 I2 deg DEd Degree of Declination (J2000) 21- 22 I2 arcmin DEm Arcminute of Declination (J2000) 24- 27 F4.1 arcsec DEs Arcsecond of Declination (J2000) 29- 33 F5.2 mag Vmag The V band magnitude 35- 38 F4.2 mag V-Ic The Johnson-Cousins V-Ic color index 40- 43 A4 --- SpT Spectral type; errors are 1 subclass (2) 45- 49 F5.1 0.1nm EWHal Low-resolution equivalent width of Hα (2) 51- 53 F3.1 0.1nm EWLi ? Equivalent width of LiI line (6707Å) (2) 55- 60 F6.2 0.1nm EWHah High-resolution equivalent width of Hα (3) 62- 65 F4.1 km/s RV Radial velocity (3) 67- 69 F3.1 km/s e_RV The 1σ error in RV (3) 71- 74 F4.1 --- R The cross-correlation process R value (4) 76 A1 --- Type [CW] Classical or Weak T Tau star (5) 78- 82 A5 --- Loc Object location (25Ori or OB1b)
Note (1): Continuing the numbering sequence from Briceno et al. (2005, Cat. J/AJ/129/907); stars from that article have CVSO numbers ≤197. The newly identified young members of 25 Ori and Orion OB1b presented here start with object CVSO-198. Note (2): Measurements from low-resolution spectra (FAST, Hydra, Hectospec). Note (3): Measurements from the high-resolution Hectochelle spectra. Note (4): A measurement of the ratio of the peak of the cross-correlation to the estimated noise, and is therefore an indicator of the accuracy of the results (Tonry & Davis, 1979AJ.....84.1511T). Note (5): The classification is based on spectral dependent threshold W(Hα) following White & Basri (2003ApJ...582.1109W). Stars CVSO-200, 238 and 246 have no low-resolution spectra available yet. They were classified as T Tauri stars from the Hectochelle spectra based on the following criteria: having the appropriate magnitudes and colors, radial velocity within 1-σ of the peak of the velocity distribution for their location, peculiar Hα emission, either a blue-shifted absorption component to Hα or this line very strongly in emission (the later is the case for CVSO-238).
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 04-Apr-2009
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